I also can't fathom how they stayed on the shelves after Vegemite was invented. It's the superior black toast tar.
And I'm not just saying that because I'm Australian and eat Vegemite off a spoon.
I was raised on Marmite, and promite, and I found them disgusting. Genuinely thought all the black yeast biproducts were the same, mum was of the opinion that "we have Vegemite at home" when what we had was Dick Smith's Ozemite.
Was introduced to name brand Vegemite in my late teens and finally understood why this product has survived capitalism. It's so fucking good.
I've never tried bovril (was raised vegetarian, and developed an alpha-gal allergy later in life), but I've definitely tried every application you can think of for Vegemite - it's good in gravy, including making a vegetarian "beef tea" and "Vegemite cordial" for hot days.